Epoxy acrylates

ABSTRACT

Novel epoxy acrylates and carboxyl group-containing epoxy acrylates of formulae II and III of the claims that are relatively highmolecular and are chemically crosslinkable can be used in photoresist formulations with the additional use of highly polymerized polymer binders. Such resist formulations are used in particular in the field of printed circuit boards and printing plates, are applicable from aqueous medium, are almost tack-free and have very good edge coverage, especially on conductors.

The present invention relates to novel epoxy acrylates of highermolecular weight and to novel polymolecular carboxyl group-containingepoxy acrylates, to the preparation thereof, to the use of saidacrylates in photoresist formulations, and to the use of saidformulations, in particular in the field of printed wiring boards andprinting plates.

Epoxy acrylates are known in abundance and are also used, inter alia, incompositions used as photoresist formulations, for example in GB 2 175908, in which resins derived from an unsaturated polybasic acidanhydride and a reaction product of an epoxy acrylate and an unsaturatedmonocarboxylic acid are used.

Formulations for solder resists that contain reaction products of epoxynovolak resins with acrylic acid and cyclic carboxylic anhydrides aredisclosed, inter alia, in EP 0 273 729. They are developable in aqueousalkaline media and have good thermal resistance and photosensitivity.Their resistance to chemicals, however, is unsatisfactory.

EP 0 418 011 discloses compositions for solder masks that are likewisebased on reaction products of epoxy cresol novolaks with acrylic acidand cyclic dicarboxylic anhydrides, using 0.4 to 0.9 equivalent ofacrylic acid per equivalent of epoxy group, such that the final productsimultaneously contains acid and epoxy groups in the same molecule. Asecond thermal crosslinking reaction between these two functionalitiesis thereby made possible in the application of these resistcompositions. The problem here is, however, aside from the preparationof the products (danger of gelation in the reaction with the anhydride),the storage stability, as the formulation containing such reactionproducts has a certain reactivity even at room temperature.

All these cited epoxy acrylates are quite generally relativelylow-molecular.

Photochemically or thermally cured epoxy acrylates that are derived fromlow molecular epoxy resins and epoxy novolaks are known for their goodthermal and mechanical properties as well as for their good resistanceto aggressive chemicals. However, the tackiness and edge coverage of theresist films obtained with these systems on conductors owing to thefairly low relative molar mass are unsatisfactory. In practicalapplication it is therefore often necessary to avoid these shortcomingsby adding highly polymerised polymer binders. Such binders normallycontain no functional acrylate groups and do not react concurrentlyduring the photochemical or thermal cure, i.e. they are not incorporatedas "passive" components in the network and therefore result in adilution of the network density, which, in turn, adversely affects inparticular the resistance to chemicals and the electrical properties ofprocessed resist layers. Furthermore, the photosensitivity decreases asa consequence of the "dilution" of the acrylate groups. The addition ofhighly polymerised polymer binders induces high viscosity of theseformulations even if the solids content is relatively low and thereforeoften results in serious problems in coating.

Japanese patent Kokai Hei 04-294352 discloses the modification ofepoxy-novolak resins by reaction with an unsaturated monocarboxylic acidand subsequently with an unsaturated anhydride of a polycarboxylic acidand the use thereof in photosensitive aqueous formulations.

It is therefore the object of this invention to provide acrylates thatdo not have the shortcomings referred to above.

This object is achieved in the practice of this invention by novel epoxyacrylates and novel carboxyl group-containing epoxy acrylates of highermolecular weight which, when used in resist formulations, are able tofunction without or with only minor amounts (<10% by weight) ofadditional polymer binders. They are obtained by reaction of so-called"advanced" epoxy resins with, typically, (meth)acrylic acid.

Specifically, the invention provides novel epoxy acrylates of formula II##STR1## wherein M is the group of formula ##STR2## R₁ is --H or --CH₃,R₂ --H, --CH₃ or phenyl, R is C₁ -C₄ alkyl or halogen, preferably CH₃ orBr,

x is an integer from 0 to 3, preferably 0 or 1, and

Y is a linking group of formula ##STR3## wherein R₃ and R₄ are eachindependently of the other hydrogen or C₁ -C₄ alkyl, or R₃ and R₄,together with the linking carbon atom, form a 5- or 6-memberedhydrocarbon ring, and the aromatic radicals of the linking group Y areunsubstituted or substituted by halogen or C₁ -C₄ alkyl,

X is --S--, --O--, or --SO₂ --, and

n is an integer from 0 to 300, preferably from 0 to 30,

with the proviso that at least 10 mol % of the radicals M have thestructure of formula ##STR4## in which R₁ and R₂ are as defined above.

If the aromatic radicals of the linking group Y are substituted, thensuitable halogen substituents are fluoro, chloro and, preferably, bromo;and suitable C₁ -C₄ alkyl substituents are straight-chain or branched C₁-C₄ alkyl groups such as methyl, ethyl, n- and isopropyl, n-, sec- andtert-butyl.

Particularly preferred linking groups Y have the formula ##STR5##wherein R₃ and R₄ are as defined above and, in particular, have theformulae ##STR6##

Preferred epoxy acrylates have the formula II, wherein R is --H (forx=O) or --CH₃, R₁ is --H or --CH₃, R₂ is --H, x is 0 or 1, n is aninteger from 0 to 30, and Y is a linking group of formula ##STR7##wherein R₃ and R₄ are --H or C₁ -C₄ alkyl and the aromatic radicals ofthe linking group are unsubstituted or substituted by halogen or C₁ -C₄alkyl.

The novel epoxy acrylates of formula II may be obtained by reacting anadvanced epoxy novolak of formula I ##STR8## wherein R, Y, n and x areas defined for formula II, with an ethylenically unsaturatedmonocarboxylic acid, if necessary in the presence of a catalyst and of apolymerisation inhibitor, at elevated temperature.

The advanced epoxy novolaks of formula I are known (q.v. inter alia JPpatent Kokai Hei 1-195056) and are prepared from a bisphenol of formulaHO--Y--OH, wherein Y is as defined above, and an epoxy novolak, in knownmanner, the molar amount of bisphenol being conveniently 0.01 to 0.1 molper epoxy group in the epoxy novolak.

These advanced epoxy novolaks of formula I carry secondary aliphatichydroxyl groups.

The reaction of the advanced epoxy novolaks of formula I to give thenovel epoxy acrylates of formula II is carried out in known manner,conveniently by reaction with an ethylenically unsaturatedmonocarboxylic acid of formula ##STR9## Suitable acids are crotonicacid, cinnamic acid and, preferably, acrylic acid or methacrylic acid ora mixture thereof. R₁ and R₂ have the meanings given above.

It is preferred to use a catalyst in this reaction. Particularlysuitable catalysts are metal salts such as chromium compounds, aminessuch as triethylamine or benzyldimethylamine, also ammonium salts suchas benzyltrimethylammonium chloride, or also triphenylphosphine andtriphenylbismuth.

A solvent may be added to the reaction, as the advanced epoxy resins offormula I are in the form of solids. However, the solvent must be inertto the educt. Suitable solvents include: ketones such as acetone, methylethyl ketone, cyclohexanone; esters such as ethyl and butyl acetate,ethoxyethyl acetate or methoxypropyl acetate; ethers such asdimethoxyethane and dioxane; aromatic hydrocarbons such as toluene,benzene and xylenes, as well as mixtures of two or more of thesesolvents.

The temperature will conveniently be in the range from 80° to 140° C.,the reaction with acrylic acid being preferably carried out in the rangefrom 80° to 120° C. and that with methacrylic acid preferably in therange from 80° to 140° C.

A polymerisation inhibitor may also be added to the reaction medium,suitably hydroquinone, hydroquinone monomethyl ether and2,6-di-tert-butyl-p-cresol.

It is desirable to introduce air or a mixture of nitrogen/oxygen intothe reaction medium, as some of the aforementioned polymerisationinhibitors are effective only in the presence of oxygen. Depending onthe amount of ethylenically unsaturated monocarboxylic acid used, epoxyacrylates of formula II that are completely or only partially acrylatedare obtained. The monocarboxylic acid can be used in equimolar amountswith respect to the epoxy groups or in less than equivalent amount. Thecompletely reacted epoxy acrylates contain almost no more epoxy groups.

The novel epoxy acrylates of formula II usually need neither be isolatedfrom the reaction medium nor purified. The reaction solution can be useddirect as obtained in the synthesis.

The partially as well as the completely reacted products of formula IIcontain aliphatic hydroxyl groups originating from the reaction of theepoxy groups with the ethylenically unsaturated monocarboxylic acid.They may additionally contain aliphatic hydroxyl groups from the educt.

The completely acrylated epoxy acrylates of formula II can then befurther reacted to carboxyl group-containing epoxy acrylates of formulaIII ##STR10## wherein A is hydrogen or the group of formula ##STR11##and R₁, R₂, R, n, x and Y are as defined above for formula II and R₅ isthe radical of a cyclic anhydride of a polycarboxylic acid after removalof the anhydride radical, and at least 10 mol % of the radicals A, as informula II, have the structure of formula ##STR12##

Preferred epoxy acrylates of formula III correspond to the preferredepoxy acrylates of formula II as indicated above, and the radicals R₁,R₂, R, x, n and Y in formula III have the same preferred meanings asgiven in connection with formula II.

As the completely reacted epoxy acrylates of formula II contain almostno more epoxy groups, they can be reacted with cyclic anhydrides ofpolycarboxylic acids. In this case, the aliphatic hydroxyl groups(formula II) react with the cyclic anhydride to effect ring opening andhemiester formation. In this reaction, for each reacted hydroxyl group acarboxylic acid bonded to the resin forms. The reaction comprisesreacting the epoxy acrylate of formula II with the cyclic anhydride, inthe absence or presence of a catalyst and of a polymerisation inhibitor,at elevated temperature. The OH groups of the compounds of formula IIare completely or partially acylated, accompanied by ring opening of theanhydride. It is therefore advantageous that the epoxy acrylates offormula II contain no more epoxy groups, otherwise gelation occurs. Thereaction is known per se.

Suitable cyclic anhydrides of polycarboxylic acids typically includesuccinic anhydride, maleic anhydride, glutaric anhydride,tetrahydrophthalic anhydride, itaconic anhydride, phthalic anhydride,hexahydrophthalic anhydride, 3-methyl- and 4-methylhexahydrophthalicanhydride, 3-ethyl- and 4-ethylhexahydrophthalic anhydride, 3-methyl-,3-ethyl-, 4-methyl- and 4-ethyltetrahydrophthalic anhydride, andtrimellitic anhydride.

Preferred anhydrides are succinic, tetrahydrophthalic, hexahydrophthalicand phthalic anhydride.

Suitable catalysts typically include amines such as triethylamine,benzyldimethylamine, pyridine or dimethylaminopyridine, ortriphenylphosphine or metal salts such as chromium or zirconiumcompounds.

If desired, a solvent may be added to the reaction medium, as the epoxyacrylates of formula II are in the form of solids. The solvent must,however, be inert to the cyclic anhydride, so that hydroxylgroup-containing solvents are not suitable. The solvents cited inconnection with the reaction with the ethylenically unsaturatedmonocarboxylic acids may suitably be used, provided they contain nofunctional groups that react with anhydrides.

The reaction temperature is conveniently in the range from 60° to 140°C., and suitable polymerisation inhibitors are typically hydroquinone,hydroquinone monomethyl ether and 2,6-di-tert-butyl-p-cresol.

It is desirable to introduce dry air or a mixture of nitrogen/oxygeninto the reaction medium. In a preferred embodiment of the invention,the epoxy acrylates of formula II are further reacted, withoutisolation, in the same reactor to the derivatives of formula IIImodified with carboxyl groups.

Isolation and purification of the novel carboxyl group-containing epoxyacrylates of formula III is usually not necessary. The reaction solutioncan be further used as obtained in the synthesis.

Owing to the unsaturated groups present in the molecule, the epoxyacrylates of formula II and the carboxyl group-containing epoxyacrylates of formula III are thermally and photochemicallycrosslinkable. They can therefore be used and applied as acrylatecomponents in photoresist formulations for the production of solderresists or primary resists by known methods, as for example disclosed inSwiss patent application 2005/93-4, filed on 2nd Jul. 1993, entitled"Photopolymerisable compositions", and give resist layers havingenhanced thermal, mechanical, electrical and chemical properties. Theresist formulations prepared therefrom are used in particular in thefield of printed wiring boards as solder resists or primary resists(etch resist or galvanoresist), and of printing plates. Suitabledevelopers are aqueous as well as aqueous-organic or organic systems.Owing to the presence of carboxyl groups in the compounds of formulaIII, these systems are particularly suitable for the preparation ofaqueous-alkaline developable photoresists.

Compared with low molecular epoxy acrylates in formulations that containpolymer binders, it is surprising that formulations containing epoxyacrylates of higher molecular weight without the addition of suchpolymer binders bring about an enhancement and not a loss ofphotosensitivity, and also that no increase in tackiness results.Furthermore, use of the formulations as solder resists results inimproved edge coverage of the conductors. As no additional polymerbinders are used in such formulations, further advantages accrue withrespect to the thermal, mechanical and electrical properties and, inparticular, to the resistance to chemicals of the resist compositionsprepared therefrom. The novel epoxy acrylates of formula II and thecarboxyl group-containing epoxy acrylates of formula III have anincreased glass transition temperature.

The invention is illustrated by the following non-limitative Examples.

PREPARATIVE EXAMPLES

Advanced epoxy cresol novolaks

Example 1

4000.00 g (18.58 mol of epoxy groups) of epoxy cresol novolak ECN 1299(ex CIBA-GEIGY) are charged to the reactor and dissolved in 1780 g ofmethoxypropyl acetate (MPA) by heating to 100° C. Then 4.00 g of a 5%solution of tetramethylammonium chloride (TMAC) in ethanol are added andthe reaction mixture is stirred for 10 minutes. The temperature of theresultant clear solution is raised to 130° C. and 165.78 g (0.73 mol) ofbisphenol A are then added. The batch is reacted at 130° C. and thereaction course is followed by titration of the epoxy groups as well asby measuring the viscosity in a Brookfield viscosimeter at 25° C.,spindle #31 (for measuring the viscosity, the samples are diluted withmethoxypropyl acetate down to a solids content of 50%).

Initial values epoxy value=3.09 mol/kg viscosity=141 mPa.s

1 h reaction time: epoxy value=3.03 mol/kg

2.5 h reaction time viscosity=319 mPa.s

3.5 h reaction time: epoxy value=2.85 mol/kg

5 h reaction time: viscosity=474 mPa.s

6 h reaction time: epoxy value=2.85 mol/kg viscosity=571 mPa.s

After 6 hours at 130° C., the reaction is discontinued (after the first2 hours reaction time the values change only very little).

Analytical data of the reaction product:

solids content (dry weight): 68.4%

epoxy value (titration): 2.85 mol/kg (solution)

Brookfield viscosity, 25°; Sp.#31: 571 mPa.s (50% soln. in MPA) GPC (gelpermeation chromatography;

polystyrene calibration): Mw=16050; Mn=2059

The product conforms to formula I, wherein Y is ##STR13## x is 1, R ismethyl and n is 0 to 6. Epoxy acrylates of advanced epoxy cresolnovolaks

Example 2

(Example 1, reacted with 100 mol % of acrylic acid):

During the entire duration of the reaction a flow of air is passed inbeneath the surface with efficient stirring to ensure good distributionof the air bubbles. The air should desirably be clean, dry and oil-free.5594.90 g of the reaction product of Example 1 above (63% solution inmethoxypropyl acetate; 15.95 mol of epoxy groups), 446.50 g ofmethoxypropyl acetate and 4.67 g of 2,6-di-tert-butyl-p-cresol arecharged to the reactor and heated to 100° C. Then the remainingreactants are added, viz. 1149.00 g of acrylic acid and 93.50 ml ofNuosynchromium 5 (supplied by HARCROS-Durham Chemicals, Durham DH3 1QX,GB) (10% solution in methoxypropyl acetate).

The batch is reacted at 105°-110° C. The reaction is initiallyexothermic, so that 15 min after the start of the reaction it isnecessary to cool with a water bath.

After a reaction time of c. 45 min, the cooling bath is removed andheating is continued with an oil bath. The reaction course is followedby titration of the acid content.

Initial value: 2.19 mol/kg

1 h reaction time: 0.89 mol/kg

2 h reaction time 0.55 mol/kg

3 h reaction time: 0.09 mol/kg

5 h reaction time: 0.11 mol/kg

7.5 h reaction time: 0.065 mol/kg

After a reaction time of 7.5 h the reaction is discontinued and theproduct is drawn off warm.

Analytical data of the reaction product:

1. solids content (dry weight): 68%

2. epoxy value (titration): 0.05 mol/kg

3. acid content (titration): 0.065 mol/kg

4. Brookfield viscosity, 25°, Sp.#31: 28100 mPa.s (solution diluted to63.6% with MPA)

5. GPC: Mw=23978; Mn=3132

The product conforms to formula II, wherein x, Y and R are as defined inExample 1, M is the group ##STR14## and n is 0 to 6. Carboxylic GroupsContaining Acrylates of Advanced Epoxy Cresol Novolaks According toFormula III

Example 3

The apparatus used consists of a 5000 ml reactor equipped with stirrer,thermometer, reflux condenser and an inlet pipe for air. To inhibit thepolymerisation of the acrylates, a weak flow of air is introduced duringthe reaction below the surface. Heating is carried out with athermostatically controlled oil bath. 313.27 g (0.73 mol of OH groups)of the reaction product of Example 2 and 147.14 g of methoxypropylacetate are charged to the reactor and heated to 100° C. Then 36.37 g(0.36 mol) of succinic anhydride and 1.25 g of pyridine as catalyst areadded and the batch is reacted for 4 hours at this temperature. Thehomogeneous reaction product is further used without additionalpurification.

Analytical data of the reaction product:

1. solids content: 51%

2. acid content (titration): 0.785 mol/kg

3. viscosity (Brookfield): 2890 mPa.s at 25° C.

The product conforms to formula III, wherein x, Y and R are as definedin Example 1, R₁ and R₂ are H, n is 0 to 6 and A is 50 mol % of thegroup ##STR15## and 50 mol % of --H.

Example 4

The apparatus of Example 3 is used. 341.18 g (0.73 mol of OH groups) ofthe reaction product of Example 2 (solids content=69.2%) and 204 g ofmethoxypropyl acetate are charged to the reactor and heated to 105° C.Then 72.33 g (0.475 mol) of tetrahydrophthalic anhydride and 1.55 g ofpyridine as catalyst are added and the batch is reacted for 8 hours at110° C. The homogeneous reaction product is further used withoutadditional purification.

Analytical data of the reaction product:

1. solids content: 49.7%

2. acid content (titration): 0.82 mol/kg

The product conforms to formula III, wherein x, Y, R, R₁, R₂ and n areas defined in Example 3 and A is 65 mol % of the group ##STR16## and 35mol % of --H. Advanced epoxy cresol novolaks (according to formula I)

Example 5

[Advancement with tetrabromobisphenol A]:

2000.00 g (9.29 mol of epoxy groups) of epoxy cresol novolak ECN 1299are charged to the reactor and dissolved in 940 g of methoxypropylacetate (MPA) by heating to 100° C. Then 2.00 g of a 5% solution oftetramethylammonium chloride (TMAC) in ethanol are added and the batchis stirred for 10 minutes. The temperature of the clear solution israised to 130° C. and 200.00 g (0.36 mol) of tetrabromobisphenol A areadded. The batch is reacted at 130° C. and the reaction course isfollowed by titration of the epoxy groups as well as by measuring theviscosity. After 6 hours at 130° C., the reaction is discontinued.

The reaction product can be used direct for the next step.

Analytical data:

1. solids content (dry weight): 71%

2. epoxy value (titration): 2.75 mol/kg (soln.)

3. Brookfield viscosity, 25° C., sp.#31: 571 mPa.s (50% soln.)

4. GPC (polystyrene calibration): Mw=19492; Mn=2126.

Example 6

[Advancement with bis(4-hydroxyphenyl)sulfone]:

1400.00 g of ECN 1299,

627.00 g of methoxypropyl acetate,

1.40 g of 5% tetramethylammonium chloride in ethanol, and

63.42 g of bis(4-hydroxyphenyl)sulfone

are reacted in accordance with the procedure of Example 5 for 6 hours at130° C. The following analytical data are obtained for the reactionproduct:

1. epoxy value (titration): 2.88 mol/kg (solution)

2. GPC (polystyrene calibration): Mw=12863; Mn=1972

Example 7

[Advancement with 4,4'-dihydroxybiphenyl]:

200.00 g of ECN 1299,

89.00 g of methoxypropyl acetate,

0.20 g of 5% tetramethylammonium chloride in ethanol, and

6.74 g of 4,4'-dihydroxybiphenyl

are reacted in accordance with the procedure of Example 5 for 6 hours at130° C. The following analytical data are obtained for the reactionproduct:

1. epoxy value (titration): 2.82 mol/kg (solution)

Example 8

[Advancement with bisphenol A]:

1600.00 g of ECN 1299,

727.00 g of methoxypropyl acetate,

1.60 g of 5% tetramethylammonium chloride in ethanol, and

92.40 g of bisphenol A

are reacted in accordance with the procedure of Example 5 for 6 hours at130° C. The following analytical data are obtained for the reactionproduct:

1. solids content (dry weight): 67%

2. epoxy value (titration): 2.74 mol/kg (soln.)

3. GPC (polystyrene calibration): Mw=25725; Mn=2257.

Epoxy acrylates of advanced epoxy cresol novolaks (according to formulaII

Example 9

[Ex. 5, reacted with 75 mol % of acrylic acid]

During the entire duration of the reaction a flow of air is passed inbeneath the surface with efficient stirring to ensure good distributionof the air bubbles. The air should be clean, dry and oil-free.

4646.30 g of the reaction product Example 5 (c. 70% solution inmethoxypropyl acetate; 12.36 mol of epoxy groups), 702.70 g ofmethoxypropyl acetate and 3.91 g of 2,6-di-tert-butyl-p-cresol arecharged to the reactor and heated to 80° C. Then the remaining reactantsare added, viz. 667.90 g of acrylic acid and 78.20 ml of a 10% dilutesolution of Nuosynchromium 5 (10.00 g of commercial product+90.00 g ofmethoxypropyl acetate). The batch is reacted at 105°-110° C. and thereaction course is followed by titration of the acid content. After areaction time of 2.5 hours, the acid content is 0.00 mol/kg, thereaction is complete and the product is drawn off warm.

Analytical data:

1. solids content (dry weight): 65.40%

2. epoxy value (titration): 0.60 mol/kg

3. acid content (titration): 0.00 mol/kg

4. Brookfield viscosity, 25° C., sp.#31: 675 mPa.s (50% soln.)

5. GPC (polystyrene calibration): Mw=25084; Mn=3004.

Example 10

[Ex. 5, reacted with 10 mol % of acrylic acid]

The following components are reacted in accordance with the proceduredescribed in Example 9:

500.00 g of the dilute reaction product of Example 5 (57% solution inmethoxypropyl acetate; 1.12 mol of epoxy groups),

8.03 g of acrylic acid,

0.29 g of 2,6-di-tert-butyl-p-cresol, and

5.84 ml of Nuosynchromium 5, 10% solution in methoxypropyl acetate.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 57.40%

2. epoxy value (titration): 1.99 mol/kg

3. acid content (titration): 0.05 mol/kg

4. Brookfield viscosity, 25° C., sp.#31: 3510 mPa.s

5. GPC (polystyrene calibration): Mw=24113; Mn=2565.

Example 11

[Ex. 1, reacted with 65 mol % of acrylic acid]

The following components are reacted for 4 hours in accordance with theprocedure described in Example 9:

900.00 g of the reaction product of Example 1, (69% solution inmethoxypropyl acetate; 2.56 mol/kg of epoxy groups),

119.72 g of acrylic acid,

105.04 g of methoxypropyl acetate,

0.74 g of 2,6-di-tert-butyl-p-cresol, and

14.81 ml of Nuosynchromium 5, 10% solution in methoxypropyl acetate.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 67.40%

2. epoxy value (titration): 0.81 mol/kg

3. acid content (titration): 0.05 mol/kg

4. Brookfield viscosity, 25° C., sp.#31: 43400 mPa.s

5. GPC (polystyrene calibration): Mw=27770; Mn=28 15.

Example 12

[Ex. 8, reacted with 75 mol % of acrylic acid]

The following components are reacted in accordance with the proceduredescribed in Example 9:

200.00 g of the reaction product of Example 8 (0.548 mol of epoxygroups),

29.61 g of acrylic acid,

31.32 g of methoxypropyl acetate,

0.17 g of 2,6-di-tert-butyl-p-cresol, and

3.40 ml of Nuosynchromium 5, 10% solution in methoxypropyl acetate.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 65.20%

2. epoxy value (titration): 0.51 mol/kg

3. acid content (titration): 0.05 mol/kg

4. GPC (polystyrene calibration): Mw=44949; Mn=2997.

Example 13

[Ex. 6, reacted with 100 mol % of acrylic acid]

The following components are reacted for 8 hours in accordance with theprocedure described in Example 2:

298.00 g of the reaction product of Example 6 (0.854 mol of epoxygroups),

61.60 g of acrylic acid,

52.00 g of methoxypropyl acetate,

0.27 g of 2,6-di-tert-butyl-p-cresol, and

5.42 ml of Nuosynchromium 5, 10% solution in methoxypropyl acetate.

The following analytical data are obtained for the reaction product:

1. epoxy value (titration): 0.03 mol/kg

2. acid content (titration): 0.06 mol/kg,

Example 14

[Ex. 7, reacted with 100 mol % of acrylic acid]

The following components are reacted for 8 hours in accordance with theprocedure described in Example 2:

295.00 g of the reaction product of Example 7 (0.83 mol of epoxygroups),

60.06 g of acrylic acid,

50.00 g of methoxypropyl acetate,

0.36 g of 2,6-di-tert-butyl-p-cresol, and

5.34 ml of Nuosynchromium 5, 10% solution in methoxypropyl acetate.

The following analytical data are obtained for the reaction product:

1. epoxy value (titration): 0.06 mol/kg

2. acid content (titration): 0.00 mol/kg.

Carboxyl group-containing acrylates of advanced epoxy cresol novolaks(according to formula III)

Example 15

[Ex. 2, reacted with 70 mol % of succinic anhydride]

The following components are reacted for 6 hours in accordance with theprocedure described in Example 3:

434.50 g of the reaction product of Example 2 (66% solution with OHnumber=2.1 mol/kg; 0.92 mol of OH groups),

64.45 g of succinic anhydride,

41.38 g of methoxypropyl acetate, and

1.76 g of pyridine.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 65.60%

2. acid content (titration): 1.31 mol/kg.

Example 16

[Ex. 2, reacted with 80 mol % of tetrahydrophthalic anhydride with4-dimethylaminopyridine as catalyst]

The following components are reacted for 7 hours in accordance with theprocedure described in Example 3:

500.00 g of the reaction product of Example 2 (1.04 mol of OH groups),

126.83 g of tetrahydrophthalic anhydride,

76.83 g of methoxypropyl acetate, and

0.23 g of 4-dimethylaminopyridine

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 48.40%

2. acid content (titration): 1.02 mol/kg

4. Brookfield viscosity, 25° C., sp.#31: 2340 mPa.s

Example 17

[Ex. 2, reacted with 65 mol % of phthalic anhydride]

The following components are reacted for 8 hours in accordance with theprocedure described in Example 3:

328,80 g of the reaction product of Example 2 (0.70 mol of OH groups),

67.86 g of phthalic anhydride,

194.77 g of methoxypropyl acetate, and

1.48 g of pyridine.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 43.90%

2. acid content (titration): 0.88 mol/kg.

Example 18

[Ex. 13, reacted with 65 mol % of tetrahydrophthalic anhydride]

The following components are reacted for 6 hours in accordance with theprocedure described in Example 3:

398,80 g of the reaction product of Example 13 (0.85 mol of OH groups),

89.00 g of tetrahydrophthalic anhydride,

190.00 g of methoxypropyl acetate, and

1.68 g of pyridine.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 51.10%

2. acid content (titration): 0.95 mol/kg.

Example 19

[Ex. 14, reacted with 65 mol % of tetrahydrophthalic anhydride]

The following components are reacted for 4.5 hours in accordance withthe procedure described in Example 3:

400,00 g of the reaction product of Example 14 (0.83 mol of OH groups),

86.76 g of tetrahydrophthalic anhydride,

211.20 g of methoxypropyl acetate, and

1.76 g of pyridine.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 46.00%

2. acid content (titration): 0.91 mol/kg.

Epoxy methacrylates of advanced epoxy cresol novolaks (according toformula II)

Example 20

[Ex. 1, reacted with 50 mol % of methacrylic acid

The following components are reacted for 4 hours in accordance with theprocedure described in Example 9:

300.00 g of the reaction product of Example 1 (70% solution inmethoxypropyl acetate; 2.85 mol/kg of epoxy groups; corresponds to 0.855mol of epoxy groups),

36.80 g of methacrylic acid,

37.96 g of methoxypropyl acetate,

0.25 g of 2,6-di-tert-butyl-p-cresol, and

4.94 ml of Nuosynchromium 5, 10% solution in methoxypropyl acetate.

The following analytical data are obtained for the reaction product:

1. solids content (dry weight): 64.80%

2. epoxy value (titration): 1.10 mol/kg

3. acid content (titration): 0.00 mol/kg

4. Brookfield viscosity, 25° C., sp.#31: 27000 mPa.s

5. GPC (polystyrene calibration): Mw=28981; Mn=2809,

Application Examples

General procedure:

The coating substrates used are cleansed copper-clad electroniclaminates or processed printed circuit boards with conductive pattern.The resist formulations are prepared by mixing and dissolving thecomponents listed in the Examples, followed by optional filtration. Alloperations are carried out under protective yellow light.

For test purposes, the formulations can be coated on to the printedcircuit board with a wire applicator. For larger series, curtain coatingmethods or roller coating as well as screen printing are used.

Drying is carried out in a circulating air oven. Exposure is made usinga commercial apparatus with 5000 W mercury high-pressure radiationsource doped with metal halide. Development is carried out in commercialcontinuous development apparatus. Assessment of photosensitivity andresolution is made by exposure through a Stouffer step wedge andresolution wedge and the result is evaluated from the developed resistimage.

Formulation 1.1 comprises a novel epoxy acrylate:

80.00 g of the reaction product of Example 2 corresponding to Example 4(as 50% solution in methoxypropyl acetate);

13.00 g of Sartomer 295 (pentaerythritol tetraacrylate)

3.00 g of Irgacure 907 (photoinitiator; CIBA AG, Basel);

1.50 g of Quantacure ITX (isopropylthioxanthone; sensitiser);

0.15 g of Orasol blue GN (dye sold by CIBA AG, Basel);

Formulation 1.2: Comparison Example with a highly polymerised binder andwithout novel epoxy acrylate:

133.33 g of Scripset 550E solution (30% solution in methoxypropylacetate; polymer binder sold by Monsanto; styrene/maleic acidcopolymer);

13.00 g of Sartomer 295;

3.00 g of Irgacure 907;

1.50 g of Quantacure ITX;

0.15 g of Orasol blue GN.

Result

    ______________________________________                                                              Formulation 1.2                                                   Formulation 1.1                                                                           (Comparison)                                            ______________________________________                                        solids content                                                                            59%               38.2%                                           viscosity 25° C.                                                                   2200   mPa.s      3000  mPa.s                                     (Epprecht)                                                                    dry layer thickness                                                                       121    μm      12    μm                                     drying conditions                                                                         5      min 80° C.                                                                        5     min 80° C.                         exposure    150    mJ/cm.sup.2                                                                              150   mJ/cm.sup.2                               development 1%     Na car-    1%    Na car-                                                      bonate 35° C.                                                                           bonate 35° C.                      last visible wedge                                                                        11                2-3                                             step                                                                          ______________________________________                                    

Formulation 1.1 containing the novel epoxy acrylate (Example 4) has alower viscosity than formulation 1.2, despite the substantially highersolids content. The photosensitivity with 11 imaged wedge steps is verymuch higher than when using comparison formulation 1.2 with only 2 to 3imaged wedge steps.

What is claimed is:
 1. An epoxy acrylate of formula II ##STR17## whereinM is the group of formula ##STR18## R₁ is --H or --CH₃, R₂ --H, --CH₃ orphenyl, R is C₁ -C₄ alkyl or halogen,x is an integer from 0 to 3, and Yis a linking group of formula ##STR19## wherein R₃ and R₄ are eachindependently of the other hydrogen or C₁ -C₄ alkyl and the aromaticradicals of the linking group Y are unsubstituted or substituted byhalogen or C₁ -C₄ alkyl, X is --O--, or --SO₂ --, and is an integer from0 to 300, with the proviso that at least 10 mol % of the radicals M havethe structure of formula ##STR20## in which R₁ and R₂ are as definedabove and with the proviso that the advanced epoxy novolak of formula I##STR21## used as starting material for the preparation of the epoxynovolak of the above-identified formula II is obtained by polyadditionof a bisphenol of formula HO--Y--OH to the epoxy novolak in a molaramount of bisphenol being 0.01. to 0.1 mol per epoxy group in the epoxynovolak, wherein Y, R, and x in formula I have the above definitions. 2.An epoxy acrylate of formula II according to claim 1, wherein R is --Hor --CH₃, R₁ is --H or --CH₃, R₂ is --H, x is 0 or 1, n is an integerfrom 0 to 30, and Y is a linking group of formula ##STR22## wherein R₃and R₄ are --H or C₁ -C₄ alkyl and the aromatic radicals of the linkinggroup are unsubstituted or substituted by halogen or C₁ -C₄ alkyl.
 3. Anepoxy acrylate of formula II according to claim 1, wherein Y is alinking group of formula ##STR23##
 4. An epoxy acrylate of formula IIaccording to claim 1, wherein R₁ is --H or --CH₃ and R₂ is --H.
 5. Aprocess for the preparation of an epoxy acrylate of formula II asclaimed in claim 1, which comprises reacting an advanced epoxy novolakof formula I ##STR24## wherein R, Y, n and x are as defined in claim 1,with an ethylenically unsaturated monocarboxylic acid, in the absence orpresence of a catalyst and of a polymerisation inhibitor, at elevatedtemperature.
 6. A method for preparing photoresist formulationscomprising the use of an epoxy acrylate of formula II as claimed inclaim 1 as acrylate component.